The magnetic strueture of magnetite erystals was investigated by the powder pattern method. The patterns on the three prineipal planes were studied. It was found that the patterns formed on the tetragonal plane consist of irregular curves and that those on the digonal and trigonal planes consist of two and five sets of parallel lines respectively. By reversing the direction of the applied field the positions of the lines were changed. This indieates that the magnetite crystal has a magnetically periodical structure.With regard to the shape of the elementary domains, MeKechan and Elmore's bloek model is preferred to Müller and Steinberg's layer structure.